New circular construction source unveiled in Spain
15.01.2026ACCIONA Agua, in collaboration with the ICARUS project, has begun the installation of a Rotating Belt Filter (RBF) pilot unit at the Sant Celoni Wastewater Treatment Plant (WWTP) aiming to recover cellulose-rich sludge from urban wastewater.
Rotating Belt Filter (RBF) pilot unit at the Sant Celoni Wastewater Treatment Plant (WWTP).
© Carla Vazquez Gomara / ACCIONA Agua
The RBF technology is designed to separate and recover cellulose fibres, in the case of the WWTPs, mainly originating from toilet paper, which makes up a large share of the organic matter entering wastewater systems. To put it in perspective, an estimated 81 rolls of toilet paper are consumed per person per year in Catalonia alone, this would be enough to wrap the Earth more than 350 times.
“By turning what was once considered waste into a high-value material, we are contributing to both resource efficiency and environmental protection. The RBF pilot will demonstrate how wastewater treatment can play a direct role in supporting the circular economy,” said Mireia Marcé Escalé from the innovation Department at ACCIONA AGUA.
Through the RBF pilot, a cellulosic sludge will be recovered and subsequently treated to obtain cellulosic fibres. Once extracted, these fibres will be, recycled for use in construction materials, such as composites or fibre-reinforced products. This approach not only reduces the amount of sludge that needs to be managed but also ensures that the recovered material is sterilised and free from contaminants, preventing their transfer into the environment. If successful, the results could have a significant impact on the construction industry, which currently accounts for 50 % of raw material extraction in the EU.
The pilot is part of the ICARUS project, which develops and tests innovative technologies to recover and reuse critical materials from industrial and municipal waste streams. In addition to the RBF installation, ICARUS partners will also conduct comprehensive analyses of contaminants and metals in the sludge to ensure the highest environmental and safety standards.
